As an image forming device for a printer, a facsimile, a reproducing unit, a plotter, and a multifunctional unit having these functions, an inkjet recording device is known as a liquid ejection recording-type image forming device which uses a recording head including a liquid ejection head (a liquid droplet ejection head) that ejects an ink droplet, for example. The liquid ejection recording-type image forming device ejects an ink droplet from the recording head to a sheet to be conveyed (not limited to paper and includes an OHP sheet, representing what the ink droplet and other liquid, etc., can be adhered to; also called a medium to be recorded on, or a recording medium, recording paper, a recording sheet) to perform image forming (recording, print, imaging, printing also used interchangeably). The liquid ejection recording-type image forming device includes a serial-type image forming device which ejects liquid droplets while the recording head moves in a main scanning direction and a line-type image forming device with the use of a line-type head which ejects droplets while the recording head does not move to perform image forming.
Herein, a liquid ejection-type “image forming device” represents a device which ejects liquid to a medium such as paper, thread, fiber, cloth, leather, metal, plastic, glass, wood, ceramics, etc., while “image forming” represents not only providing a medium with an image which has a meaning (e.g., character or graphics), but also providing a medium with an image which does not have a meaning (merely causing a droplet to impact the medium. Moreover, “ink” is not limited to what is called ink, but all types of liquids which can perform image forming, such as what is called recording liquid, fixing solution, liquid, etc., and includes DNA sample, resist, pattern material, resin, etc., for example. Furthermore, “image” is not limited to a planar image (two-dimensional image), but also an image provided to what is formed three-dimensionally, and also an image formed by three-dimensionally shaping a solid itself.
There is known a liquid ejection head such that a nozzle plate having multiple nozzle holes (also called nozzles, nozzle openings, orifices, ejection ports, etc.); a flow channel plate (also called a chamber plate, etc.) including pressure generating chambers (also called pressure chambers, liquid chambers, pressurizing liquid chambers, an individual liquid chamber, etc.), each of which communicates with the corresponding nozzles and a fluid resistance section which supplies ink to each of the pressure generating chambers; and a vibrating plate member which forms wall faces of the pressure generating chamber, the fluid resistance section, etc. that are adhesively joined, and a vibrating plate which forms the wall face of the pressure generating chamber that is deformed by a pressure generating unit such as a piezoelectric element to change the volume within the pressure generating chamber, thus causing liquid droplets to be ejected from the nozzle holes (Patent document 1).
Due to the need for stabilizing the liquid droplet in order to obtain a higher image quality, positional accuracy and shape accuracy of the above-described nozzle holes of the liquid ejection head, which holes are formed at a pitch of print resolution, or a pitch of ⅓ to ½ thereof, need to be made high.
As a related art method of manufacturing the nozzle plate, a method is known to form a tapered cross-sectional shape by form rolling by punching a thin metal plate and then grind and form a tip portion to be a nozzle hole.
Moreover, as a method of manufacturing the flow channel plate, there is a method of accurately processing a pressure generating chamber by isotropic etching using monocrystalline silicon (Patent document 3). However, when the size of a head exceeds one inch, there is a problem that material cost increases. Moreover, when the flow channel plate formed of a silicon material is bonded with the nozzle plate formed by the above-mentioned processing method, for example, when hardening is done at high temperature as it is to be done in a short time, since linear expansion coefficients of the materials are different, a problem of a mismatch in opposing positions of the respective plates, warping, or, possibly cracking of the silicon material occurs, so that an adhesive which hardens at room temperature must be used, leading to a problem that the process of manufacturing the head takes time.
Thus, it is known to form the flow channel plate by forming a through hole on a metal thin plate by etching (Patent document 4), or to form, by press working, a pressure generating chamber in a narrow and long groove (Patent document 5), or to form, using press working, an ink flow channel hole to be a pressure generating chamber (Patent document 6). The above-described methods of manufacturing make it possible to form the nozzle plate, the flow channel plate, and the vibrating plate member all with the same material, for example, a stainless steel thin plate, for example.
Moreover, if an air bubble remains within a common liquid chamber (common liquid flow channel) which supplies liquid to the nozzle, the individual liquid chamber, and multiple individual liquid chambers when the liquid is filled or supplied into the head, it is not possible to stably eject the liquid droplets. Moreover, an increase in the number of nozzles which eject the liquid droplets lead to a further demand for speedily replenishing the liquid from the common liquid chamber to the individual liquid chamber, so that an inability for the replenishment to catch up with the need thereof causes a droplet ejection failure.
In order to increase an air bubble dischargeability in the liquid ejection head, there is disclosed in a related art document (Patent document 7), for example, that a ceiling section which makes up a liquid flow channel successively includes regions I, II, and III from an ejection port side in accordance with a height from a bottom face section which makes up the liquid flow channel; the regions I and III are parallel to the bottom face section which makes up the liquid flow channel; a liquid flow channel in the region I is higher than the liquid flow channel in the region III; the region II has an inclination increasing in the height of the liquid flow channel from the region III to the region I; the region II is formed within the range of distance L1-L2 from a reference point which is an intersection between the ceiling section and an ejection port forming face; the bottom face section has an ejection pressure generating unit within the range of distance LH1-LH2 from a projection point of the reference point onto the bottom face section; and a relationship between the ceiling section and the bottom face section meets a predetermined relational expression.
Moreover, Patent document 8 discloses a liquid droplet ejection head having a piezoelectric element, wherein near edges of an ink inlet and an ink outlet of a pressure chamber are formed respectively in corresponding projecting sections extending inside along the longitudinal direction of the pressure chamber, thus enhancing an ink flow rate, and making it easier to discharge an air bubble.
Furthermore, Patent document 9 discloses filling a curing material in a step section formed in a flow channel, and smoothing a flow channel inner wall, thus preventing an air bubble from remaining and a pressure wave from attenuating in the step section.
Patent Documents
Patent document 1: JP7-156387
Patent Document 2: JP2002-113529
Patent Document 3: JP2007-144706
Patent Document 4: JP2004-153478
Patent Document 5: JP2000-263799
Patent Document 6: JP2007-152663
Patent document 7: JP3495863
Patent Document 8: JP2006-205621
Patent Document 9: JP2008-74034